[mythtv-users] Number of tuners

Stephen Worthington stephen_agent at jsw.gen.nz
Sat Mar 1 01:47:35 UTC 2014

On Fri, 28 Feb 2014 16:34:45 -0800, you wrote:

>Not to be confused with the ongoing thread "tuner numbering". :-)
>I have an HDHR Prime. I have the three tuners in it configured in mythtv 
>backend. When I look at the Information > System screen on the frontend, 
>I see six tuners. Is that normal? If it's not, is there something I 
>should do to fix it?

The System Information > Tuner Status screen shows all the multirec
virtual tuners, not the physical tuners.  Digital transmitters
(DVB-S/S2, DVB-T/T2, DVB-C?, ATSC?) are capable of transmitting
multiple TV channels at once on each frequency by sending streams of
numbered data packets.  Each TV channel has at least a video stream
and an audio stream, and there can be other streams for a channel (eg
closed captions), and there can be other streams not associated with a
channel (eg EIT EPG, pay-TV entitlements).  The numbering on the
packets tells what stream they belong to, and to record a channel the
receiver just selects out the packets for the streams that belong to
that one channel and writes them to disk.  So it is easy for a
receiver to select out the streams for multiple channels and write
them to separate files on disk at the same time.

In MythTV, the mechanism for this is the multirec virtual tuners. When
you set up a physical tuner in mythtv-setup > Capture Cards >
Recording Options, you will find a setting for "Max recordings".  That
specifies the number of multirec virtual tuners to be created for that
physical tuner.  The limit is currently 5 (for 0.27).  Each multirec
tuner can record one channel from its associated physical tuner.  The
physical tuner can only be tuned to one frequency at a time, so the
associated virtual tuners can only record from the channels being
broadcast in the digital streams on the one transmitter frequency at

So, it looks like you have the "Max recordings" value set to 2 for
each of your 3 physical tuners.  Depending on your recording habits
and how the channels you record from are spread around the transmitter
frequencies, that may be causing you to waste physical tuners by
having multiple physical tuners tuned to the same frequency when you
need to record more than two channels from the same frequency.  I have
all my tuners set up with the maximum value of 5.

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